Cap with tamper evident seal for containers, container comprising said cap and preform for producing said container

ABSTRACT

There is described a container ( 1 ) with a thread ( 5 ) for a screw closing cap ( 3 ). The container has a neck ( 1 A) with a lower shoulder ( 1 X) that extends from the external surface ( 1 Z) of the neck, on which the thread ( 5 ) is formed toward the inside.

TECHNICAL FIELD

The present invention relates to plastic containers, in particularplastic bottles for natural mineral water, or plastic bottles forsparkling mineral water and also for other beverages.

STATE OF THE ART

The use of plastic bottles for packaging mineral water or otherbeverages is very widespread. Plastic bottles are normally provided witha screw cap, or capsule, which is engaged to the bottle and which has atamper evident seal or security band that is broken when the bottle isopened for the first time and provides the consumer with a guarantee ofthe integrity of the bottle content at the time of purchase.

Modern large bottling plants fill tens of thousands of bottles per day,and in some cases hundreds of thousands of bottles and consequently theyconsume a large number of this type of container. There is constantsearch for new ways of reducing the weight of each bottle and of eachcap, firstly to reduce production costs and secondly to also reduce theenvironmental impact of this type of packaging, considered that not allplastic bottles are recycled.

Plastic bottles of this type normally have a threaded neck and, betweenthe thread and the body of the bottle, two perimeter collars or annularridges, the one used to couple the tamper evident seal and the other tohandle the bottles in the filling plants.

EP-A-2207722 describes a plastic bottle wherein the neck of the bottlehas only one perimeter collar or annular ridge used both to engage thebottle with handling and conveying members inside the filling plant, andto constrain the tamper evident seal. To allow handling of the bottle,between the threaded neck of the bottle and the annular ridge there isprovided an annular groove or recess in which the mechanical handlingmembers engage.

The use of a single perimeter collar or annular ridge, in place of theconventional conformation with double collar, enables the weight of eachbottle to be reduced by a few grams and consequently the quantity ofplastic used each year by the packaging plant to be reduced by manytons.

WO-A-2009/146567 describes a cap with tamper evident seal for a bottle,said cap comprising a lateral wall and an internal thread formed on aninternal surface of the lateral wall. The lateral wall of the capcomprises a security element in the form of a tab that cooperates withthe thread of the bottle, so as to be irreversibly altered when thescrew cap is removed from the bottle. The bottle is provided with acollar placed between the body of the bottle and the thread.

These known systems have reduced the quantity of plastic used to producebottles and caps. However, there is still a margin for improving thisaspect and further reducing the quantity of plastic material required toproduce each bottle.

SUMMARY OF THE INVENTION

The invention provides for a container, typically a plastic bottle, forexample and in particular for water or other beverages, comprising: abody; a substantially cylindrically shaped end portion or neck, formingan opening mouth; a thread, formed on an external surface of said endportion, for engaging a closing cap. Between the body of the containerand the end portion or neck there is provided a guiding shoulder toguide the container in the packaging plants.

In this way the collar or annular ridge normally provided on the neck ofthe container, between the thread and the body of the container, isomitted. This results in a reduction of the plastic material required toproduce the container, both because the neck can be shorter, and becausethe plastic material forming the projecting collar is no longernecessary.

Advantageously, the end portion or neck of the container extends fromthe mouth of the container up to said guiding shoulder. Preferably, theshoulder has an external diameter equal to the diameter of the externalsurface of the end portion or neck of the container and an internaldiameter smaller than the external diameter and equal to the minimumdiameter of a shoulder connecting the end portion or neck to the body ofthe container.

According to some embodiments, the thread has at least one stop surfacefor cooperating with a security element of a closing cap of thecontainer.

According to another aspect, the invention relates to a systemcomprising a screw cap and a container, typically a bottle, as describedabove.

According to yet another aspect, the invention relates to a preform forproducing a plastic container, typically a bottle, as described above.In some embodiments, the preform comprises a main body and asubstantially cylindrical end portion or neck, having a radial dimensiongreater than the radial dimension of the body of the preform (whereradial dimension of the body of the preform is preferably intended asthe minimum radial dimension of this body, if it has a variabledimension) and having a thread formed on an external cylindrical surfaceof the end portion or neck. Between the end portion or neck and the bodyof the preform there is provided a shoulder intended to form a guidingsurface of the container, said shoulder extending radially inward fromthe substantially cylindrical surface of the end part or neck of thepreform.

According to a different aspect, the invention provides for a screw capfor a container comprising a lateral wall and an internal thread formedon an internal surface of the lateral wall, characterized in that thelateral wall comprises a security element configured to be irreversiblyaltered when the screw cap is removed from the container. The securityelement is permanently altered, for example deformed or broken, when thecap is unscrewed, as a result of interference with the external threadof the container, for example a bottle. A tamper evident seal is thusobtained without the need to use an additional band on the cap andrelated collars on the bottle. A reduction of the length or height ofthe end portion or neck of the bottle of around 6-7 mm, typically around6.5 mm, is also obtained. In this area, the thickness of the plasticmaterial is around 1 mm. This results in a substantial saving of plasticmaterial, with considerable reduction of costs and environmental impact.

In advantageous embodiments of the cap, the security element is arrangedin an intermediate position of the lateral wall, between an end edge anda front wall of the cap. It can have a portion projecting from theinternal surface of the lateral wall toward a rotation axis of the cap.For example, the security element can comprise a tab projecting towardthe inside of the .cap. In advantageous embodiments, the tab extendstangentially and preferably with an inclination corresponding to theinclination of the thread. The tab can be housed in a cutout or slitprovided in the lateral wall of the cap and can be fastened at aproximal end thereof to the wall, while the distal end can projecttoward the internal volume of the cap, so as to interfere with theexternal thread of the bottle or other container.

Further features and embodiments of the invention are describedhereunder and are defined in the appended claims, which form an integralpart .of the present description.

Features and embodiments are disclosed here below and are further setforth in the appended claims, which form an integral part of the presentdescription. The above brief description sets forth features of thevarious embodiments of the present invention in order that the detaileddescription that follows may be better understood and in order that thepresent contributions to the art may be better appreciated. There are,of course, other features of the invention that will be describedhereinafter and which will be set forth in the appended claims. In thisrespect, before explaining several embodiments of the invention indetails, it is understood that the various embodiments of the inventionare not limited in their application to the details of the constructionand to the arrangements of the components set forth in the followingdescription or illustrated in the drawings. The invention is capable ofother embodiments and of being practiced and carried out in variousways. Also, it is to be understood that the phraseology and terminologyemployed herein are for the purpose of description and should not beregarded as limiting.

As such, those skilled in the art will appreciate that the conception,upon which the disclosure is based, may readily be utilized as a basisfor designing other structures, methods, and/or systems for carrying outthe several purposes of the present invention. It is important,therefore, that the claims be regarded as including such equivalentconstructions insofar as they do not depart from the spirit and scope ofthe present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood by following the description andaccompanying drawing, which shows a non-limiting practical embodiment ofthe invention. More in particular, in the drawing:

FIG. 1 shows a side view of the upper part of a bottle with a capaccording to the invention;

FIG. 2 shows a side view of the cap of FIG. 1;

FIG. 3 shows a section according to of FIG. 2;

FIG. 4 shows a side view of the neck of the bottle, with the capremoved;

FIG. 5 shows a section according to V-V of FIG. 4;

FIG. 6 shows a section according to VI-VI of FIG. 4, with the additionof the cap applied to close the mouth of the bottle, screwed on andintegral;

FIG. 7 shows the section of FIG. 6 after the cap has been at leastpartly unscrewed and the security element has been broken;

FIG. 8 shows a preform for producing a bottle of the type shown in FIG.4;

FIG. 9 shows an improved preform for producing a bottle of the typeshown in FIG. 4; and

FIGS. 10 and 11 show sections analogous to the sections of FIGS. 6 and 7in a further embodiment.

DETAILED DESCRIPTION OF AN EMBODIMENT

The following detailed description of the exemplary embodiments refersto the accompanying drawings. The same reference numbers in differentdrawings identify the same or similar elements. Additionally, thedrawings are not necessarily drawn to scale. Also, the followingdetailed description does not limit the invention. Instead, the scope ofthe invention is defined by the appended claims.

Reference throughout the specification to “one embodiment” or “anembodiment” or “some embodiments” means that the particular feature,structure or characteristic described in connection with an embodimentis included in at least one embodiment of the subject matter disclosed.Thus, the appearance of the phrase “in one embodiment” or “in anembodiment” or “in some embodiments” in various places throughout thespecification is not necessarily referring to the same embodiment(s).Further, the particular features, structures or characteristics may becombined in any suitable manner in one or more embodiments.

Hereinafter, specific reference will be made to an embodiment whereinthe plastic container is a bottle, for example a bottle for beverages,such as mineral water or the like. However, it must be understood thatthe concept on which the invention is based can also be embodied inother types of plastic containers with similar requirements andtechnical-functional characteristics similar to those of bottles forwater and/or beverages.

In FIG. 1 a plastic bottle for water and/or beverages of other type isindicated with 1, while the cap of the bottle, in the closedarrangement, is indicated with 3. The neck or upper end portion of thebottle 1 is indicated with 1A. The body of the bottle is indicated with1B and the shoulder between neck 1A and body 1B is indicated with 1S.

FIG. 4 shows an enlargement of the neck 1A of the bottle without the cap3. Around the neck 1A of the bottle 1, below the mouth 1C and on theexternal cylindrical surface 1Z of the neck 1A, there is formed anexternal thread 5 that can comprise one or more threads 5A. Each threadcan have one or more breaks 5B. In fact, in some embodiments each thread5A is discontinuous and broken in one or more points or break areas 5B.On the one hand this enables a reduction in the plastic materialrequired to produce the bottle and on the other it facilitates operationof the security cap, as will be explained below.

More in particular, the bottle 1 has no collar between neck 1A and body1B of the bottle 1. It has a shoulder 1S that joins the main body 1B ofthe bottle to the upper part or neck 1A, on the external cylindricalsurface 1Z of which, having an external diameter DM, the thread 5 isformed.

The cylindrical portion forming the neck 1A of the bottle ends at thebottom with an undercut or shoulder 1X, below which the shoulder 1S ofthe bottle is connected. The undercut or shoulder 1X forms an annularsupporting surface, with a major diameter equal to the diameter DM ofthe cylindrical portion 1A forming the neck of the bottle and a minordiameter indicated with Dm. The annular shoulder of radial dimension(DM−Dm)/2 thus formed is sufficient to provide a guiding surface forhandling the bottle in the filling plants. The shoulder 1X formedstarting from the external cylindrical surface of the end portion orneck 1A toward the axis of the bottle 1 in substance replaces the collarnormally provided on prior art bottles, which projects radially outwardwith respect to the cylindrical surface on which the thread of thebottle is produced.

The shape of the bottle 1 shown in FIG. 4 enables a reduction in thequantity of plastic material required to produce the bottle with respectto conventional solutions. In fact, on the one hand the collar that isusually provided between the thread of the neck of the bottle and thebody of the bottle is eliminated. By eliminating the collar, thequantity of plastic required to form it is also eliminated. Moreover, asthere is no collar, the axial length of the neck of the bottle can bereduced. The axial length of the portion of neck 1A of the bottle ofFIG. 4 (between thread 5 and shoulder 1S of the bottle) is substantiallyless (by several millimeters) than the neck of conventional bottles,which are provided with at least one and, in some cases, with twocollars.

In some embodiments, the diameter DM and the diameter Dm can be such asto form a shoulder 1X with a radial dimension of around 3-4 mm, forexample around 3.5 mm. For example, the diameter DM can be in the orderof 22-23 mm and the diameter Dm can be in the order of 15-16 mm. Theheight of the cylindrical portion 1A forming the neck of the bottle canbe in the order of 12-20 mm, for example around 15 mm.

This different shape of the upper part of the bottle implies, inconventional bottles for mineral water or beverages, a reduction inweight of around 2-2.5 g per bottle. Modern bottling plants produceseveral tens of thousands of bottles per hour and therefore a reductionof around 2 grams of plastic on each bottle implies a very large savingof plastic material, with economic advantages for the manufacturer and areduction of environmental impact. For example, in a bottling plant thatproduces 80,000 bottles per hour, modification of the upper part of thebottle described above implies a saving of around 160-176 kg/hour ofplastic, which in a continuous processing plant implies a daily savingof 3840-4224 kg/day of plastic and consequently of 1400-1542 tons/yearof plastic. This leads to a corresponding reduction of the quantity ofplastic disposed of as waste and/or recycled. With regard to cost, inthe case of PET, which currently costs 1,180 Euro per ton, the annualsaving is of around 1,650,000-1,820,000 Euro.

The cap 3 can generally have an axial-symmetrical shape, with axis A-A.The cap 3 can comprise a lateral wall 7 extending from an end edge orlower edge 9 to a front wall or upper wall 11 of the cap 3. The lateralwall 7 has an external surface 7A and an internal surface 7B. Along theinternal surface 7B an internal thread 13 is provided, which comprisesone or more threads 13A. The internal thread 13 is configured tocooperate with the external thread 5 provided on the neck 1A of thebottle 1.

The height H of the cap 1, i.e. the dimension in axial direction of thecap 3, can advantageously be such that, when the cap 3 is screwed ontothe bottle 1, the edge 9 of the cap is approximately positioned at theshoulder 1X formed between the cylindrical portion 1A and the shoulder1S of the bottle 1.

Along the extension of the lateral wall 7, i.e. between the edge 9 andthe front wall 11, in the wall 7 there is housed a security element, ortamper evident element, i.e. a member designed to interact with thebottle 1 and indicate whether the bottle has been opened. The securityelement replaces the conventional security band or tamper evident bandprovided on prior art caps. In the drawing, the security element isindicated as a whole with 15. In some embodiments, the security ortamper evident element 15 comprises a tab 17 and a cutout or slit 19formed in the lateral wall 7 and extending for the whole of thethickness thereof, i.e. open on both the internal 7B and external 7Asurfaces of the lateral wall 7.

In some embodiments, the tab 17 and the slit or cutout 19 are orientedapproximately tangentially, i.e. they have a larger dimension in thecircumferential or perimeter direction of the wall 7 and a smallerdimension in the axial direction.

In advantageous embodiments, the tab 17 and the slit or groove 19 areoriented approximately in the direction of the threads 13A of theinternal thread 13. Advantageously, the tab 17 and the respective cutoutor slit 19 that houses it are arranged in the groove between twoadjacent threads 13A, as can be seen in particular in FIGS. 2 and 3.When the cap 3 is screwed onto the neck of the bottle 1, the tab 17 andthe related cutout or slit 19 are thus arranged at a thread 5A of theexternal thread 5 of the bottle.

In practice, on the internal face of the cap, the tab 17 can be fullyhoused in the slit or cutout 19, with the exception of a distal end 17A.In substance, the tab 17 is set back with respect to the internalsurface 7B or flush there with, except for the distal end 17A. Theopposite end of the tab 17, labled with 17B and hereinafter namedproximal end 17B, is fastened to the material forming the wall 7 of thecap 3. Between the distal end 17A and the proximal end 17B of the tab 17there extends the main body of the tab 17. The thickness of the body ofthe tab can correspond substantially to the thickness of the lateralwall 7.

Therefore, in practice in some embodiments the tab 17 is constituted byan elongated portion of the same material forming the wall 7 of the cap3, joined to the wall 7 at the proximal end 17B, while the remainingpart is separated from the wall 7, but housed in the thickness of thelateral wall 7 inside the slit or cutout 19.

The distal end 17A of the tab 17 is generally shaped so as to interferewith the neck of the bottle 1 when it is unscrewed, so as to cause apermanent visible alteration of the tab 17. The shape of the distal end17A is also such as to enable initial screwing of the cap 3 onto thebottle 1 without deformation or permanent alteration of the tab 17. Inthis way the tab 17 acts as a security or tamper evident element thatindicates if the bottle has been opened, enabling the user to checkwhether the bottle is integral, for example at the time of purchase.

In some embodiments, along the main body of the tab 17, between thedistal end 17A and the proximal end 17B, an incision 17C is providedthat forms a preferential bending or breaking point, for purposes thatwill be explained below. In some embodiments, a second preferentialbending or breaking point can be provided at the proximal end 17B of thetab 17, as can be seen in particular in FIGS. 6 and 7. The incision 17Ccan be formed on the external surface of the tab, as shown in thedrawing, or on the internal surface thereof. Likewise, an internal orexternal incision can also be provided at the proximal end 17B of thetab, as shown in the drawing. It would also be possible for both aninternal and an external incision to be provided.

In some embodiments, the distal end 17A of the tab 17 has an end surface17D that extends toward the inside of the cap 3, i.e. toward the axisA-A of said cap, beyond the internal surface 7B of the lateral wall 7.The end surface 17D can be radial, or inclined with respect to theradial direction, as shown in the drawing.

In advantageous embodiments, the innermost corner of the end surface 17Dis joined to the body of the tab 17 by means of a second surface 17Efacing the inside of the cap 3. In practical embodiments, the connectionsurface 17E can be curved, or flat, as shown by way of example in FIGS.6 and 7. When the cap is integral (FIG. 6) the surface 17E is moreinclined than the surface 17D with respect to the radial direction. Theconnection corner between the two surfaces 17D and 17E projects towardthe inside of the cap 3, i.e. beyond the internal surface 7B of thelateral wall 7.

When the cap is screwed onto the bottle, as can be seen in FIG. 6, thedistal end 17A of the tab 17 projects toward the neck 1A of the bottle 1and is inserted in one of the breaks 5B of the external thread 5.

In advantageous embodiments, at least at some of the breaks 5B, thecorresponding thread 5A has a stop surface 5C inclined with respect tothe radial direction and forming an undercut. As can be seen inparticular in FIG. 6, the orientation of the front surface 17D of thetab 17 and the orientation of the stop surface 5C of the thread 5A, atthe break 5B of which the distal end 17A of the tab 17 is positioned,are such that when the cap is unscrewed, according to the arrow F (FIGS.6, 7), the distal end 17A of the tab 17 abuts in the undercut formed bythe stop surface 5C and the rotation of the cap causes outwarddeformation (arrow f17, FIG. 7) of the tab 17. Deformation isfacilitated by the facilitated deformation or breaking point 17C in thecentral area of the body of the tab and by the facilitated deformationor breaking point at the proximal end 17B of the tab 17, where thisjoins to the wall 7 of the cap 3.

Rotation of the cap 3 in the direction of unscrewing (arrow F), causestherefore a permanent deformation or breakage of the tab. This condition(FIG. 7) is easily detectable from the outside of the bottle and of thecap. The tab 17 thus forms a security or tamper evident element thatreplaces the conventional tamper evident band. The user is able todetermine the integrity of the bottle by observing or touching the tab17.

The function of security or tamper evident element is obtained withoutthe need to manufacture a tamper evident band along the lower edge 1A ofthe cap and therefore reducing the quantity of material required toproduce the cap. The need for a collar on the bottle, which in prior artbottles has the sole function of cooperating with the tamper evidentband, is also eliminated. This also contributes to limiting the quantityof plastic used to produce the bottles.

FIG. 8 schematically shows a preform used to produce the bottle 1. Thepreform has a body 1P, intended to form the body of the bottle, thepreformed portion 5P with the external thread 5 and the shoulder 1X. Thepreformed portion 5P constitutes an end portion or neck 1A, whichcorresponds to the end portion or neck 1A of the bottle 1. The externalsurface 1Z of the end portion or neck 1A is substantially cylindrical.The thread 5 projects radially outward from the cylindrical surface 1Z,of the end portion or neck 1A, while the shoulder 1X extends radiallyinward from the lower edge of the external cylindrical surface 1Z, withdiameter DM, until reaching the minimum diameter Dm.

In some embodiments, under the shoulder 1X the preform has a shape thatincreases in diameter, to facilitate subsequent molding of the finishedbottle.

FIG. 9 schematically shows an improved preform for producing a bottle ofthe type described above. Also in this embodiment, the preform has abody 1P, destined to form the body of the bottle, the preformed portion5P with the external thread 5 and the shoulder 1X. The body 1Ppreferably has a constant external diameter from the shoulder 1X to thebottom of the preform, indicated with 1F. This external diameter isequal to the minor diameter Dm of the shoulder 1X of the bottle 1.

In some embodiments the security system of the present invention can bemade more efficient by the presence of a breakable constraining elementbetween the tab 17 and the wall 7 of the cap. This additional element isillustrated by way of example in a modified embodiment, shown in FIGS.10 and 11, which show sections similar to those of FIGS. 6 and 7. Thesame numbers indicate parts equal or equivalent to those describedabove. In FIGS. 10 and 11, reference 17F indicates a breakableconstraining element, which joins the tab 17 to the edge of the cutoutor slit 19 formed in the wall 7.

In some embodiments, the element 17F has the form of a bridge and can beformed at the distal end of the tab 17.

When the cap 3 is unscrewed, the deformation of the tab 17 causestearing of the bridge 17F. This provides the user with an even clearerindication of the fact that the container is not integral.

In some embodiments, the bridge 17F or other breakable element can beplaced in a different position, for example along the lateral extensionof the tab 17, rather than at the distal end thereof. It would also bepossible to provide more than one breakable element, for example morethan one bridge 17F, in various points of the tab 17.

The embodiments described above and illustrated in the drawings havebeen discussed in detail as examples of embodiment of the invention.Those skilled in the art will understand that many modifications,variants, additions and omissions are possible, without departing fromthe principles, concepts and teachings of the present invention asdefined in the appended claims. Therefore, the scope of the inventionmust be determined purely on the basis of the broadest interpretation ofthe appended claims, comprising these modifications, variants, additionsand omissions therein. The terms “comprise” and its derivatives do notexclude the presence of further elements or steps besides thosespecifically indicated in a given claim. The term “a” or “an” precedingan element, means or characteristic of a claim does not exclude thepresence of a plurality of these elements, means or characteristics.When a device claim lists a plurality of “means”, some or all of these“means” can be implemented by a single component, member or structure.The stating of given elements, characteristics or means in distinctdependent claims does not exclude the possibility of said elements,characteristics or means being combined with one another. Any referencenumbers in the appended claims are provided to facilitate reading of theclaims with reference to the description and to the drawing, and do notlimit the scope of protection represented by the claims.

1. A system comprising: a container comprising a body, a substantiallycylindrically shaped end portion or neck forming an opening mouth, and athread formed on an external surface of said end portion for engaging aclosing cap, wherein a guiding shoulder is provided between the body ofthe container and the end portion for guiding the container in packagingplants, said guiding shoulder having an external diameter equal to adiameter of the external surface of the end portion of the container;and a screw cap for said container, said screw cap comprising a lateralwall and an internal thread formed on an internal surface of the lateralwall, wherein said lateral wall comprises a security element configuredto be irreversibly altered when the screw cap is removed from thecontainer, wherein the screw cap is devoid of a tamper evident bandalong an end edge of said screw cap.
 2. The system as claimed in claim1, wherein said end portion or neck extends from the opening mouth ofthe container to said guiding shoulder.
 3. The system as claimed inclaim 1, wherein said shoulder has an internal diameter, smaller thanthe external diameter and equal to a minimum diameter of a shoulderconnecting the end portion or neck to the body of the container.
 4. Thesystem as claimed in claim 1, wherein said thread has at least one stopsurface to cooperate with a security element of a closing cap.
 5. Thesystem as claimed in claim 1, wherein said security element is arrangedin an intermediate position of the lateral wall of the cap, between anend edge and a front wall of the cap.
 6. The system as claimed in claim1, wherein said security element is projecting from the internal surfaceof the lateral wall toward a rotation axis of the cap.
 7. The system asclaimed in claim 1, wherein said security element comprises at least onebreakable element, which is broken when the cap is unscrewed from thecontainer.
 8. The system as claimed in claim 1, wherein said securityelement is configured to interfere with the thread of the container whenthe cap is unscrewed from the container and suffer permanent deformationvisible from an outside of the cap, as a result of interference betweenthe security element and the container.
 9. The system as claimed inclaim 1, wherein said security element comprises a tab formed in saidlateral wall and having a distal end projecting toward an inside of thelateral wall to cooperate with the thread of the container, said tabcomprising a proximal end, fastened to the lateral wall of the cap,opposite said distal end, said tab further comprising; an intermediatebody normally housed in a seat produced in said lateral wall, the distalend projecting from said seat toward the inside of the lateral wall. 10.The system as claimed in claim 9, wherein said tab extends tangentiallyalong said lateral wall.
 11. The system as claimed in claim 1, whereinsaid security element comprises a tab, wherein a distal end of the tabhas a front surface configured and arranged to abut against a stopsurface produced on a thread of the container with which the cap isengaged, when the cap is unscrewed from the container.
 12. The system asclaimed in claim 1, wherein said security element comprises a tab, saidtab being joined to the lateral wall by at least one breakable element.13. A preform for producing a plastic container for a system accordingto claim 1, the preform comprising: a main body and a substantiallycylindrical end portion or neck, said substantially cylindrical endportion or neck having a radial dimension greater than a radialdimension of the main body and said substantially cylindrical endportion or neck having a thread formed on a substantially cylindricalexternal surface of the substantially cylindrical end portion or neckhaving an external diameter; a shoulder between the substantiallycylindrical end portion or neck and the main body for forming a guidingsurface of the container, said shoulder having a major diameter equal tothe external diameter of said substantially cylindrical external surfaceand extending radially inward from the substantially cylindricalexternal surface of the substantially cylindrical end portion or neck ofthe preform towards the main body of the preform.
 14. The system asclaimed in claim 10, wherein said tab comprises an extensionsubstantially parallel to the thread of the cap.
 15. The system asclaimed in claim 11, wherein the front surface is oriented approximatelyradially.
 16. The system as claimed in claim 12, wherein said at leastone breakable element is formed by a bridge that joins the tab to anedge of a cutout or slit produced in said lateral wall and in which thetab is housed.
 17. The preform of claim 13, wherein the shoulder doesnot project radially outwardly beyond the external diameter of thesubstantially cylindrical external surface of the substantiallycylindrical end part or neck.